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Wheel wear profiles are interesting for both economic and performance reasons. A good wheel profile design should be able to resist wear and to allow stable vehicle running. The ability to resist wear reduces the wheel reprofiling and replacement cost. The ability to allow stable vehicle running is important for safety and ride quality. In this work, a wear model based upon the work done in the wheel/rail contact patch is used to predict wheel wear profiles. The effects of train dynamic response, random rail alignment and the non-linearity of wheel/rail contact geometry are included The distribution of contact patch work is obtained by discretized method and applied to the wheel wear problem. Using the contact patch work wear model, consecutive wheel wear profiles for tread contact and slight flange contact are predicted. These analytical wear profiles match well with experimental results and other analytical approaches. / Master of Science

A method is presented for the prediction of the wear history of a train wheel by a numerical simulation. The method consists of three fundamental steps. First, the wheel/rail contact geometry is characterized. Contact points, Herzian contact patch area and creep coefficients are determined as functions of the wheelset lateral position. Second, a time history of the wheelset positions and velocities is determined from a simulation of the vehicle response to a specified track input. Finally, a wear algorithm dependent on the geometry and the dynamics is used to compute the amounts of material to be removed at the discrete points describing the wheel profile. The process is repeated recurrently to simulate the gradual wearing of the wheel. The method has been tested with several different wear models and it has been found that worn profiles are relatively insensitive to the selection of wear model. A parametric study on the effect of creep coefficient and payload on wear rate has been used to differentiate the wear models. Results include predictions of AAR and CN worn wheel profiles. The predictions show that the CN profile wears parallel to the new profile. This trend has been observed in practice. / M.S.

The effect of friction stir processing (FSP) on the mechanical wear behavior was investigated for Ti-1Al-8V-5Fe (Ti-185) and stainless steel (Incoloy® A-286) alloys. The Ti-185 and A-286 alloys were tested in different processing conditions, including as rolled (AR), AR+FSP, and AR+FSP+aged. A high frequency reciprocating rig was used to simulate fretting-type wear of these alloys at room temperature. The Vickers micro-hardness and wear rates were calculated and compared for each processing condition. It was determined that along with increasing hardness in the stir zones, FSP resulted in improved wear resistance for both alloys. Specifically, wear rates in the stir zones were reduced to lowest values of 1.6 x 10-5 and 5.8 x 10-7 mm3/N·m for the AR+FSP+aged Ti-185 and A-286 alloys, respectively, despite lower hardness for A-286 alloy. Mechanistic studies were conducted to determine the reason behind these improvements in wear resistance and the effect of FSP on the microstructural evolution during wear. For the Ti-185 alloy, x-ray diffraction revealed that there was a phase transformation from β-Ti (AR+FSP) to α-Ti (AR+FSP+aged). This phase decomposition resulted in the harder and stiffer Ti phase responsible for lowering of wear rate in Ti-185. While x-ray diffraction confirmed the A-286 alloy retains its austenitic structure for all conditions, scanning electron microscopy revealed completely different wear track morphology structures. There was increased coarse abrasion (galling) with the AR+aged A-286 alloy compared to the much finer-scale abrasion with the AR+FSP+aged alloy, which was responsible for smaller and less abrasive wear debris, and hence lower wear rate. Furthermore, cross-sectional focused ion beam microscopy studies inside the stir zone of AR+FSP+aged A-286 alloy determined that a) increased micro-hardness was due to FSP-induced microscopic grain refinement, and b) the corresponding wear rate decrease was due to even finer wear-induced grain refinement. With both effects combined, the level of damage and surface fatigue wear was suppressed resulting in lowering of the wear rate. In contrast, the absence of FSP-induced grain refinement in the AR+aged A-286 alloy resulted in lower hardness and increasing wear rate. In addition, micro-Raman spectroscopy inside the stir wear zone determined that the wear debris contained metal oxides of Fe3O4, Cr2O3, and NiO, but were a consequence and not the cause of low wear. Overall, FSP of titanium and stainless steel alloys resulted in lowering of wear rates suggesting it is a viable surface engineering technique to target and mitigate site-specific wear.

Call number: LD2668 .T4 1978 R37 / Master of Science

New computer technologies are applied to the classical material engineering two-body abrasive wear process. The computer simulation provides an interactive and visual representation of the wear process. The influence of grit size, grit tip radius and load (at constant workpiece hardness and tool path) on the wear rate, wear coefficient and wear surface topography is predicted. The simulation implements microcutting and microploughing with material displacement to the sides of the groove. The validation of the simulation is demonstrated by comparing with the previous modelling literature and with experiments. / Thesis (M.Sc.)-University of Natal,Durban, 2002.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / by Kwai-Yung Benjamin Su. / Sc.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Vita. / Includes bibliographical references. / by Bruce M. Kramer. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Doreen Joan Blanchard. / M.S.

Wear to mining equipment reduces operational efficiency. If wear rates can be predicted, appropriate matching of alloys to the mine' s geologic conditions can aid in improving the operational efficiency. This study addresses rock characteristics which lead to wear. Macroscopic rock tools which lead to wear include sharp edges and comers on rocks. During a rock/equipment interaction, these rock tools cause high point pressures on the surface of the equipment which leads to ductile cutting and gouging of the surface and subsequent removal of metal. Hard mineral grains, or grain tools, produce abrasion as the grains move across equipment surfaces. Grain and rock tools were analyzed for metamorphic, hydrothermally altered, plutonic, and sedimentary rocks from six mines and quarries. Grain tools were examined by petrographic analysis and Knoop microhardness: rock tools by uniaxial compressive tests, density, and rock size. Fourier analysis of rock and mineral shapes and abrasion tests were used to examine the evolution of tools. Prediction of wear rates appears most closely related to uniaxial compressive strength, Knoop microhardness, and quartz content. Uniaxial compressive strength relates to rock tool endurance; Knoop microhardness contrast between mineral grains and matrix/cement influences evolution of tools during surface interactions; quartz content relates to the abrasive capacity of a rock surface.